Why is the number of eggs laid by frogs at a time much higher than those laid by a hen
Answers
Actually it's the way to survive in this world(remember the quote 'survival of the fittest'!?) one organism follows. The main two factors in the replication of any organism are Quality and Quantity. In this case frog chose quantity and the hen chose quality.
Higher organisms always follow the trend to choose quality over quantity. Compared to other classes Mammals have always lesser number of offspring while the insects have the most.
In this case as frogs have external fertilization, it's the wiser way to choose number of eggs over quality of it. Adverse environmental factors, interruption by predators during mating etc factors always play important roles in replication of this organisms. But in case of hen the chances of being affected by this superficial factors are much less, thus they chose quality over quantity.
Now if you consider human and hens, humans generally give birth to 1 or 2 babies( it can vary upto maximum 10) in their whole lifetime but a hen gives lot more eggs than that in its lifetime(got the analogy?).
The number of eggs laid by frogs at a time are much higher than those laid by a hen because of the following reasons:
1) We can see External fertilization in frog but not in hen.
2) Due to external fertilization, the female frog lays a vast number of eggs in water & males releases millions of sperms on to them.
3) The eggs produced may be carried to a long distance by water currents or may be eaten by predators.